This invention relates to a method and apparatus for the agglomeration and compaction of iron bearing materials utilizing a continuous process employing ram compactors and known solids handling and mixing equipment. The method is particularly effective in compaction of steel plant waste materials and hazardous wastes.
This invention relates further to iron and steel making, wherein iron bearing materials are reduced of oxygen by chemical extraction or liberation with a media, and wherein the processing results in solid iron-bearing materials considered as wastes being ejected from the system and thereupon discarded. These materials are discarded since no commercial process is in operation that economically justifies their recovery.
Presently available commercial processes and equipment for compaction of steel plant wastes are not capable of providing a useful non-hazardous product without hot compaction. The method is also effective for the recovery and use of steel mill waste materials, reducing the environmental hazards associated therewith.
In some cases where economic considerations are justified, waste materials can be agglomerated into pellets for reintroduction to the feed system. In most other cases, waste materials are considered as loss materials and discarded. In direct reduction, wherein iron bearing material is reduced through chemical extraction of oxygen, the present state of the art dose not include any method of agglomeration of the product for economical handling and export.
Although great amounts of money have been spent on these developments, no commercial plants have been built for the recovery of steel plant waste or the economical production of agglomerated direct reduced iron. Thus, this invention applies to the economical recovery and use of iron and steel mill waste, the economical agglomeration of direct reduced iron, the production of other products using both the aforementioned materials and additives to produce feed materials for ferro alloy production, iron and steel mill charges, recovery of hazardous steel mill wastes, recovery of iron and steel mill wastes, and compaction to direct reduced iron.
In this invention, materials handling and mixing equipment known to the industry and known ram briquetting equipment collect, feed, mix, distribute and agglomerate iron bearing material. By the invented process, in-plant iron-bearing materials and wastes associated with iron and steel mills and associated with direct reduced iron materials are treated and handled. The compositions of materials are in the form and consist of iron ore fines and dust, direct reduced iron fines and dust, direct reduced iron, slurry sludge of iron bearing materials, mill scale, and other waste materials in iron and steel mills, such as lime dust and coal or coke dust as an additive or other additives such as silica, manganese, or any other materials and alloys and in combinations with the intent to make products and for the purpose of handling and treating in plant wastes. Manufacturing plants which utilize iron or iron-bearing materials, such as nail making plants, can also use the process for handling of turnings, borings, clippings, iron-bearing scrap, and other in-plant wastes. Further use of the invented process is to treat direct reduced iron, by cold compaction for the purpose of export of direct reduced iron products without additives in an economical manner conducive to presently operated direct reduced iron plants.
In recent years, many reduction plants normally associated with iron and steel mills have been installed worldwide. In most cases, the direct reduction plants have been designed with excess capacity, despite the state of iron and steel overcapacity in the world. Since the direct reduction of iron is a separate process for the extraction and purification of the iron, and the DRI product is to be used as feed stock for iron and steel processes, direct reduced iron is available in excess capacity from those installations. However, in order to take advantage of the excess capacity, the direct reduced iron product must be treated in a manner for shipping and storage that is convenient to use as feed stock. To be stored, one must consider the well known phenomenon of reoxidation (including catastrophic reoxidation) of direct reduced iron as well as consider environmental concerns of the generation of dust and fines. Processes have been developed and are in commercial operation for entire direct reduction plants, but there is no available means to handle excess production capacities due to economic constraints and high cost of capital investment.
Recently, the use of iron bearing materials in the form of fines, pellets and natural lump has generated a major impact on the economics of the facility by the accumulation of large amount of iron bearing wastes. No commercial process is in operation to handle or treat these wastes and plant-generated fines.
This invention is a process for the treatment, handling, and agglomeration of those iron and steel mill wastes, the agglomeration of excess direct reduced iron, the manufacturing of other products as feed source materials for the iron and steel mill industry, contained in a single process and equipment designed to be scaled down or up depending on the economic considerations of the plant and materials to be treated.
The process of this invention has great flexibility and may be used to mix and feed various materials to produce a product to the consistency of iron and steel mill requirements. The invented process allows the recovery of iron and steel mill in-plant wastes, treatment and agglomeration of direct reduced iron and production of feed materials for the ferro alloy industry, utilizing a single process which requires no additions for any product changes.